1. Field of the Invention
The present invention relates to a light-emitting device having a light-emitting element and a plurality of phosphors, as well as a vehicle lamp including the light-emitting device. The light-emitting device prevents a color of light during illumination from significantly differing from a color exhibited during non-illumination.
2. Description of Related Art
A vehicle lamp, which includes a light source that is a light-emitting device (such as a light-emitting diode (LED)) and a plurality of lamp units (each unit being formed of a lens, a reflection mirror, and the like), is known. A desired light distribution pattern can be obtained by combining a unit of a direct-projection type and a unit of a reflection type (see, e.g., Japanese Patent Publication 2004-95480).
However, when a white light-emitting diode is used as a light source of a lamp, it is difficult to obtain light having a wide wavelength range solely from an LED chip. Therefore, there are employed, e.g., an LED chip for emitting blue light, and a phosphor which is excited by some of blue light originating from the LED chip (hereinafter called a “blue-light-excited phosphor”). More specifically, blue light is generated from the LED chip, and a yellowish—which is a complementary color of the blue light—light is generated from the phosphor; and white light can be obtained by means of mixing the two types of light.
However, the above-described configuration involves a problem arising from a difference between a light color of the light-emitting device during illumination and a color which is exhibited externally during non-illumination.
For instance, in a state where the light-emitting element (the LED chip) is not lighting, the blue-light-excited phosphor exhibits a color tone (yellow) under external light (visible light). Therefore, in a case where the light-emitting element is used as a light source of a lamp, when reflection by way of an optical component, such as a lens or a reflection mirror, is excessive, there may arise problems, such as pseudo lighting or nonconformance with lamp specifications. For example, when a yellow component exhibited on a front face of the lamp is close to a functional color of a turn signal lamp, or the like, a problem such as false-recognition may arise depending on an extent of reflection by an optical component.
To this end, means, such as arrangement of the lamp's optical design or provision of a filter, are adopted for preventing development of a color tone during non-illumination of the lamp. However, in order to employ such means, certain problems must be solved, such as influences exerted during illumination on a light color or a light distribution pattern, or problems caused by employment of the means, such as an increase in the complexity of the configuration, or a cost increase.
The present invention aims at preventing a light color of a light-emitting device during illumination from differing from a color exhibited externally during non-illumination, thereby removing an obstacle to application of the light-emitting device as a vehicle lamp.